84 research outputs found
The U(1)-Higgs Model: Critical Behaviour in the Confinig-Higgs region
We study numerically the critical properties of the U(1)-Higgs lattice model,
with fixed Higgs modulus, in the region of small gauge coupling where the Higgs
and Confining phases merge. We find evidence of a first order transition line
that ends in a second order point. By means of a rotation in parameter space we
introduce thermodynamic magnitudes and critical exponents in close resemblance
with simple models that show analogous critical behaviour. The measured data
allow us to fit the critical exponents finding values in agreement with the
mean field prediction. The location of the critical point and the slope of the
first order line are accurately given.Comment: 21 text pages. 12 postscript figures available on reques
Phase diagram of d=4 Ising Model with two couplings
We study the phase diagram of the four dimensional Ising model with first and
second neighbour couplings, specially in the antiferromagnetic region, by using
Mean Field and Monte Carlo methods. From the later, all the transition lines
seem to be first order except that between ferromagnetic and disordered phases
in a region including the first-neighbour Ising transition point.Comment: Latex file and 4 figures (epsfig required). It replaces the preprint
entitled "Non-classical exponents in the d=4 Ising Model with two couplings".
New analysis with more statistical data is performed. Final version to appear
in Phys. Lett.
Mixing patterns in networks
We study assortative mixing in networks, the tendency for vertices in
networks to be connected to other vertices that are like (or unlike) them in
some way. We consider mixing according to discrete characteristics such as
language or race in social networks and scalar characteristics such as age. As
a special example of the latter we consider mixing according to vertex degree,
i.e., according to the number of connections vertices have to other vertices:
do gregarious people tend to associate with other gregarious people? We propose
a number of measures of assortative mixing appropriate to the various mixing
types, and apply them to a variety of real-world networks, showing that
assortative mixing is a pervasive phenomenon found in many networks. We also
propose several models of assortatively mixed networks, both analytic ones
based on generating function methods, and numerical ones based on Monte Carlo
graph generation techniques. We use these models to probe the properties of
networks as their level of assortativity is varied. In the particular case of
mixing by degree, we find strong variation with assortativity in the
connectivity of the network and in the resilience of the network to the removal
of vertices.Comment: 14 pages, 2 tables, 4 figures, some additions and corrections in this
versio
Utilização de leveduras vivas (Saccharomyces cerevisiae) visando à produção de cordeiros Ile de France superprecoces em sistema de creep-feeding
Penicilinoterapia intravenosa em altas doses na neurossífilis: estudo de 62 casos II. Avaliação do líqüido cefalorraqueano
Demographic variation and biomass allocation of Agropyron cristatum grown on steppe and dune sites in the Hunshandake Desert, North China
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